1. Field of the Invention
The invention relates to a method and to a device for reversing the thrust of a turbojet engine having a very high bypass ratio.
Turbojet engines with high bypass ratios are well suited to subsonic flight and enable high propulsion efficiencies to be obtained for low specific fuel consumptions. Turbojet engines with very high bypass ratios of between 11 and 18 have an even better propulsion efficiency, but possess a greater mass and increased drag because of the large diameter of their fan. This type of jet engine can be made lighter by using an engine structure that has a speed reduction gear interposed between the low pressure turbine and the fan, but this structure is still heavier than a conventional engine with the same thrust. This is partly due the mass of the thrust reverser located in the large-diameter part of the nacelle.
2. Summary of the Prior Art
Conventional thrust reversers usually comprise displaceable elements, such as pivoting doors or gates, which cooperate in the deployed position to reverse the thrust.
It is also known to provide a turbomachine of the bypass type with a variable-pitch fan in which the blades can be pivoted in order to reverse the bypass flow. This arrangement is generally not as heavy as the conventional door-type or gate-type thrust reverser, but requires an expensive and complex mechanism for changing the pitch of the blades.